Vesicle Formation and Follicular Root Sheath Separation in Mice Homozygous for Deleterious Alleles at the Balding (bal) Locus

The study investigated the balding (bal) mutation in mice, an autosomal recessive mutation causing alopecia and immunologic anomalies. Researchers localized the mutation to chromosome 18 and examined histologic lesions in two alleles (bal(J) and bal(Pas)). They observed separation of the inner and outer root sheath in anagen follicles, making hair fibers easily pluckable, and vesicles in various body parts. Despite these lesions resembling human pemphigus vulgaris, no autoantibodies were detected. Normal expression of keratinocyte markers was found, but keratin 6-positive cells indicated a defect in adhesion molecules. This defect was linked to a thymidine insertion in the desmoglein 3 gene, causing a premature stop codon.